Ecology Weeks 1-5

Populations contain:

• One Species

• More than one species

Using the food web to the left, which of the following is most likely to lead the greatest decrease in the deer mouse population?

• an increase in the owl populations
• an increase in the grass population
• an increase in the pine tree population
• an increase in the cottontail population

For the food chain shown above, which of the following changes would have the most severe consequences?

• a drastic decrease in rainfall, causing drought
• a poaching of predatory hawks by game hunters
• the introduction of a second predator that eats field mice
• a parasitic infestation that reduces  the cricket population

Organisms that make up the first  level of a food chain and produce their own food are classified as 

• predators
• autotrophs
• heterotrophs
• decomposers

Which of these best describes the relationship between epiphytes and trees?

• Parasitism
• Migration
• Commensalism
• Predation

The diagram to the left is intended to show relationships in an ecosystem. What do the arrows represent?

• The direction of energy flow
• The direction of the wind
• The direction of the sun
• The direction of the predators

Nitrogen-fixing bacteria called rhizobia enter the root hairs of bean plants. The bacteria are located in small root structures called nodules. The plants provide energy to the bacteria, and in return, the plants receive nitrogen for growth from the bacteria.
According to the information above, which of these best describes the relationship between rhizobia and bean plants?

• Parasitism
• Opportunism
• Commensalism
• Mutualism

In this diagram of a marine food web, which term describes the sea turtles?

• Aquatic herbivores
• Autotrophic producers 
• Third-level consumers 
• Primary decomposers 

A sample of bacteria was added to a culture dish containing a food supply. The dish was kept in an incubator for two weeks, where temperature and other conditions that favored bacterial growth were kept constant. The graph below shows changes that occurred in the bacterial population over the two weeks. 

Which statement provides the best explanation for the changes?

• The bacteria consumed all of the available food
• The culture dish contained an antibiotic for the first five days
• The bacteria were unable to reproduce until day 8
• The temperature increased and the bacteria died

In this food web to the right the bacteria probably function as…

• Producers
• Herbivores
• Decomposers
• Carnivores